Discharge tube with dismountable electrode

ABSTRACT

Discharge tube comprising a compartment in which at least two electrodes are arranged. One electrode is kept inside the compartment by at least two wall bushings whose ends, penetrating inside the compartment, rest flexibly on the lateral wall of the electrode.

[ Oct. 16, 1973 United States Patent Roux I DISCHARGE TUBE WITHDISMOUNTABLE ELECTRODE 313/285 UX 313/285 X 313/356 X 313/356 X 313/288X 2,853,643 9/1958 lversen...................r. 3,034,009 5/1962 Zunicket :11... 2,056,034 9/1936 Brucker 3,295,000 12/ l 966 Johnson 3,560,7792/1971 May.....,... 3,588,574

Lasers, Marcoussis, France 1 F iled= FOREIGN PATENTS OR APPLICATIONS653,952 5/1951 Great Britain 313/285 348,471 10/1960Switzerland.........................313/237 21] Appl. No.: 89,220

Primary Examiner-John K. Corbin Attorney-Sughrue, Rothwell, Mion, Zinn &Macpeak ABSTRACT [52] US. 331/945 PE, 313/1 10,313/286,

[51] Int. H01s 3/00 Discharge tube comprising a compartment in which at6 54 39 U %3 1, l m 8 H 36 4 31 m3 5 m2 m8 7 m2 m .h 2 m, 2 f 7 B II3 l3 J 8 5 least two electrodes are arranged. One electrode is kept insidethe compartment by at least two wall bushings whose ends, penetratinginside the compartment, rest flexiblyon the lateral wall of theelectrode.

[56] References Cited UNITED STATES PATENTS 2 Claims, 1 Drawing Figure1,911,793 5/1933 Brandt............................ 313/285 X 2,745,9815/1956 Sanabria et 313/285 X DISCHARGE TUBE WITH DISMOUNTABLE ELECTRODEBACKGROUND OF THE INVENTION 1. FIELD OF THE INVENTION The presentinvention concerns discharge tubes, and is particularly, but notexclusively, concerned with laser discharge tubes.

2. DESCRIPTION OF THE PRIOR ART A discharge tube generally consists ofan oblong enclosure with an electrode situated at each end and betweenwhich the discharge takes place.

Several ways of disposing an electrode in a discharge tube havepreviously been proposed. In one proposal, the electrode is weldeddirectly toa support element passing through the discharge tube wall. Inanother proposal, the electrode and a support element are provided withcooperating male and female conical portions which are force fitted toone another to provide support for the electrode. In a third proposal,the electrode is provided with a portion of the same diameter as thesupport element passing through the discharge tube wall, and theelectrode is held in line with this element by means of a sleevesupported elastically on the side walls of the support element and ofthat portion of the electrode.

Such electrode mounting arrangements are not adapted to laser dischargetubes, particularly in the case where the electrode is disposed on thedischarge tube axis. When the electrode is so disposed, it must beprovided with an axial bore along the tube axis so as not to block thelaser beam. Moreover, in laser. discharge tubes the electrodes aresubjected to very high temperatures during long periods, so that theelectrodes rapidly deteriorate and must be frequently replaced.

When the electrode is provided with an axial bore, it is generallywelded to support elements disposed radially of the electrode andpassing through the discharge tube walls. When it is necessary toreplace such an electrode, it must be detached from the supportelements, and this generally involves the vaporization of a smallquantity of metal. The resulting metallic vapors can find their way onthe optical elements closing the laser tube and thus reducing theirtransmission power.

SUMMARY OF THE INVENTION The present invention is intended to reduce thedisadvantages of the previously proposed arrangements, and to provide adischargetube in which mounting and dismounting of an electrode isreadily achieved, while maintaining a monobloc discharge tube structure.

In accordance with the invention, adischarge tube contains an electrodesupported by at least one support electrode is elastically supportedwithin the enclosure. The electrode is cylindrical and has an axial borealigned with an axis of the discharge tube. The support element bearsagainst side walls of this cylinder, which is further located by spigotsstanding away from inside surfaces of the enclosure walls. An inner tubemember of the discharge tube, mounted with its axis co-incident with thedischarge tube axis, partially locates inside the axial bore in thecylindrical electrode. The discharge tube has a sleeve portion ofinternal diameter greater than the external diameter of the cylindricalelectrode and closed by a readily detachable closure element providingaccess to the electrode. The electrode is formed with a groove extendingaround its periphery in which the support element end portion orportions locate.

IN THE DRAWING The invention will now be described in more detail, byway of example only, with reference to the accompanying diagrammaticdrawing.

The single FIGURE is a longitudinal section of a discharge tube.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to the Figure, a laserdischarge tube consists of co-axial tubes 1 and 2 of which the outertube 2 is longer than the inner tube 1. These two tubes are so arrangedthat their respective ends 6 and 7 are ap proximately co-planar. Thetubes 1 and 2 are held centered by membranes 3 and 4 extending betweenthe inner wall surfaces of tube 2 and the outer wall surfaces of tube 1.

The membrane 4 isplaced as close as possible to the tube extremities 6and 7, while the membrane 3 is situated at some distance from theextremity 5 of the inner tube 1.

A cylindrical sleeve 8 is attached to the membrane 4 and carries at itsextremity an optical element of the laser tube. In theparticular'example shown in the Figure, this is a mirror 9 but it willbe appreciated that this may be replaced with other suitable elements,for example, a plate disposed at the Brewster incidence.

A support element 10 passes through thewall of the sleeve 8, and carriesat its inner end an electrode 11.

The space 12 betweentubes 1 and 2 and membranes 3 and 4 is incommunication with the interior 14 of tube 1 through an opening 13formed in the wall of this tube. This space 12 provides a chamber forholding a reserve of gas and thus contributing to an increase in thelife of the discharge tube.

The second electrode 15 of the discharge tube consists of a metalliccylinder 15 with an axial bore 16 aligned with the axis of the innertube L'The end portion of the inner tube 1 extends into this axial bore16 in the second electrode.

The electrode 15 is held in position inside the tube 2 by at least twosupport elements passing through the discharge tube wall. One of theseelements is shown at 17 and another is indicated in dotted outline. Thesupport elements 17 each have a rigid portion 19 passing through a ring18 partially closing the-end of the tube 2. Inside the discharge tube,each element 17 has an elastic portion 20 curved into a U-shaped leafspring Where the length of the cylinder providing electrode 15 is great,its opposite end portion is located within the tube 2 by means of atleast two projections standing away from the inside surface of thistube. One such projection is shown at 23, another being indicated indotted outline.

These projections extend away from the inside wall of the tube 2 so asto just contact the outer surface of the electrode 15. Deterioration ofthe tube assembly on heating is thus avoided.

On the ring 18 is mounted a sleeve 26 co-axial with the tube 2 and whoseinternal diameter is slightly greater than the greatest outside diameterof the electrode 15. The sleeve 26 is closed by an optical element 27co-operating with the element 9 to provide the laser cavity.

Since the interior 25 of the sleeve 26 is of great diameter than theelectrode 15, the latter can be inserted into the discharge tube as apenultimate stage in its fabrication, so as to guard it as long aspossible from impurities which may become attached to its surface andsubsequently migrate to the optical elements 9 and 27. When it isrequired to change the electrode 15, it is a simple matter to remove theoptical element 27 and slide the electrode out through the sleeve 26.

Preferably, three projections 23 are provided, equiangularly spacedaround the discharge tube axis.

What is claimed is:

1. A laser discharge tube comprising: 7

an enclosure including inner and outer concentric tubes defining coaxialfirst and second passages, said outer tube extending beyond said innertube at both ends and closed at said ends by optical elements to definetherewith an optical resonant cavity,

a first tubular metal electrode positioned concentrically between saidtubes and in partial telescoping position with respect to said innertube at one end thereof,

a second electrode positioned adjacent the other end of said inner tubeand within said outer tube and acting with said first electrode toeffect an electrical discharge therebetween and generate a laser beam,said discharge and said laser beam passing through said first and secondpassages, and

support means having a rigid end portion passing through said outer tubewall and having a first end portion within said enclosure bearingelastically against said first tubular electrode to effect an electricalconnection therewith and to permit removal of said first tubularelectrode and replacement during repair of said laser discharge tube.

2. The laser discharge tube as claimed in claim 1, wherein said supportmeans comprises a plurality of circumferentially spaced metal stripsupport elements bearing against said first tubular electrode atcircumferentially spaced points and said support means further includesinternal projections on said outer tube and bearing on said firsttubular electrode at axially spaced positions with respect to saidsupport elements and generally in line with said elements.

1. A laser discharge tube comprising: an enclosure including inner andouter concentric tubes defining coaxial first and second passages, saidouter tube extending beyond said inner tube at both ends and closed atsaid ends by optical elements to define therewith an optical resonantcavity, a first tubular metal electrode positioned concentricallybetween said tubes and in partial telescoping position with respect tosaid inner tube at one end thereof, a second electrode positionedadjacent the other end of said inner tube and within said outer tube andacting with said first electrode to effect an electrical dischargetherebetween and generate a laser beam, said discharge and said laserbeam passing through said first and second passages, and support meanshaving a rigid end portion passing through said outer tube wall andhaving a first end portion within said enclosure bearing elasticallyagainst said first tubular electrode to effect an electrical connectiontherewith and to permit removal of said first tubular electrode andreplacement during repair of said laser discharge tube.
 2. The laserdischarge tube as claimed in claim 1, wherein said support meanscomprises a plurality of circumferentially spaced metal strip supportelements bearing against said first tubular electrode atcircumferentially spaced points and said support means further includesinternal projections on said outer tube and bearing on said firsttubular electrode at axially spaced positions with respect to saidsupport elements and generally in line with said elements.